1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitable for an imaging optical system used for image pickup apparatus such as a digital camera, a video camera, a TV camera, a monitoring camera, and a silver-halide film camera.
2. Description of the Related Art
An imaging optical system used for an image pickup apparatus (camera) is required to be a small zoom lens having a wide angle of field and high resolution power. In addition, because various optical members such as a low pass filter and a color correction filter are arranged between a lens rearmost portion and a solid-state image pickup element, it is required that a back focus of the zoom lens is relatively long. Further, the zoom lens is required to have an image stabilizing mechanism for correcting an image blur that is generated when an accidental vibration such as shaking is transmitted to the zoom lens.
As a zoom lens having a relatively long back focus and a wide angle of field, there is known a negative lead type zoom lens including a lens unit having a negative refractive power arranged on a most object side. As the negative lead type zoom lens, there is known a four-unit zoom lens that includes a first lens unit to a fourth lens unit having negative, positive, negative, and positive refractive powers in order from an object side to an image side, and includes an image stabilizing mechanism.
A zoom lens described in Japanese Patent Application Laid-Open No. 2007-78834 includes, in order from the object side to the image side, a first lens unit to a fourth lens unit having negative, positive, negative, and positive refractive powers, in which a positive lens as a part of the second lens unit is moved in a direction perpendicular to an optical axis so as to correct image blur. In addition, there is known a five-unit zoom lens that is a negative lead type zoom lens including, in order from the object side to the image side, a first lens unit to a fifth lens unit having negative, positive, positive, negative, and positive refractive powers, and includes an image stabilizing mechanism. A zoom lens described in Japanese Patent Application Laid-Open No. 2009-251112 includes, in order from the object side to the image side, a first lens unit to a fifth lens unit having negative, positive, positive, negative, and positive refractive powers, in which the fourth lens unit is moved in the direction perpendicular to the optical axis so as to correct image blur.
When the image stabilizing lens unit is moved in the direction perpendicular to the optical axis in order to correct image blur, a zoom lens having a small and light-weight image stabilizing lens unit is required for reducing size and power consumption of the image stabilizing mechanism. For instance, if a diameter of the image stabilizing lens unit is increased, lens weight is increased, and a size of a lens frame for holding the lens is also increased. Therefore, a load is imposed on a drive system for performing image stabilization, and hence the drive system becomes large. As a result, the entire apparatus becomes large.